TOKYO, Sept. 8 (Xinhua) -- A total of 30 people have been confirmed dead, six others in state of cardiopulmonary arrest, and 13 people remain missing in the wake of a powerful earthquake that rocked Hokkaido Prefecture in northern Japan on Thursday, Japanese government said on Saturday.

The government's top spokesperson, Chief Cabinet Secretary Yoshihide Suga told a press conference on Saturday that a total of 40,000 people, including local police, firefighters, Self-Defense Force personnel and Japan Coast Guard, are searching for the missing and helping the disaster-hit areas "with all their efforts."

At one point after the powerful quake on Thursday, some 2.95 million homes in Hokkaido were without electricity as the whole prefecture suffered a power outage.

Suga said that while power was restored in most of the areas, some 20,000 households were still without electricity, and he urged homes and offices already with power to cut usage by about 10 percent.

An earthquake with a preliminary magnitude of 6.7, struck Hokkaido prefecture at 3:08 a.m. local time Thursday (1808 GMT Wednesday).

The quake logged the maximum 7 on Japan's seismic intensity scale, marking the first time for Hokkaido since the seismic scale was revised in 1996, according to Japan's weather agency.

According to public broadcaster NHK, as of 6:00 a.m. local time Saturday morning, some 30,000 households across Hokkaido were still without water supply.

As of 11:00 a.m. local time, some 12,000 people were still taking refuge in more than 430 emergency evacuation shelters across the prefecture, said the public broadcaster.